import asyncio
import asyncio.streams
import traceback
from collections import deque
from contextlib import suppress
from html import escape as html_escape
from http import HTTPStatus
from logging import Logger
from typing import (
    TYPE_CHECKING,
    Any,
    Awaitable,
    Callable,
    Optional,
    Tuple,
    Type,
    Union,
    cast,
)

import yarl

from .abc import (
    AbstractAccessLogger,
    AbstractAsyncAccessLogger,
    AbstractStreamWriter,
)
from .base_protocol import BaseProtocol
from .helpers import CeilTimeout, current_task
from .http import (
    HttpProcessingError,
    HttpRequestParser,
    HttpVersion10,
    RawRequestMessage,
    StreamWriter,
)
from .log import access_logger, server_logger
from .streams import EMPTY_PAYLOAD, StreamReader
from .tcp_helpers import tcp_keepalive
from .web_exceptions import HTTPException
from .web_log import AccessLogger
from .web_request import BaseRequest
from .web_response import Response, StreamResponse

__all__ = ('RequestHandler', 'RequestPayloadError', 'PayloadAccessError')

if TYPE_CHECKING:  # pragma: no cover
    from .web_server import Server  # noqa


_RequestFactory = Callable[[RawRequestMessage,
                            StreamReader,
                            'RequestHandler',
                            AbstractStreamWriter,
                            'asyncio.Task[None]'],
                           BaseRequest]

_RequestHandler = Callable[[BaseRequest], Awaitable[StreamResponse]]
_AnyAbstractAccessLogger = Union[
    Type[AbstractAsyncAccessLogger],
    Type[AbstractAccessLogger],
]


ERROR = RawRequestMessage(
    'UNKNOWN', '/', HttpVersion10, {},
    {}, True, False, False, False, yarl.URL('/'))


class RequestPayloadError(Exception):
    """Payload parsing error."""


class PayloadAccessError(Exception):
    """Payload was accessed after response was sent."""


class AccessLoggerWrapper(AbstractAsyncAccessLogger):
    """
    Wraps an AbstractAccessLogger so it behaves
    like an AbstractAsyncAccessLogger.
    """
    def __init__(self, access_logger: AbstractAccessLogger):
        self.access_logger = access_logger
        super().__init__()

    async def log(self,
                  request: BaseRequest,
                  response: StreamResponse,
                  request_start: float) -> None:
        self.access_logger.log(request, response, request_start)


class RequestHandler(BaseProtocol):
    """HTTP protocol implementation.

    RequestHandler handles incoming HTTP request. It reads request line,
    request headers and request payload and calls handle_request() method.
    By default it always returns with 404 response.

    RequestHandler handles errors in incoming request, like bad
    status line, bad headers or incomplete payload. If any error occurs,
    connection gets closed.

    :param keepalive_timeout: number of seconds before closing
                              keep-alive connection
    :type keepalive_timeout: int or None

    :param bool tcp_keepalive: TCP keep-alive is on, default is on

    :param bool debug: enable debug mode

    :param logger: custom logger object
    :type logger: aiohttp.log.server_logger

    :param access_log_class: custom class for access_logger
    :type access_log_class: aiohttp.abc.AbstractAccessLogger

    :param access_log: custom logging object
    :type access_log: aiohttp.log.server_logger

    :param str access_log_format: access log format string

    :param loop: Optional event loop

    :param int max_line_size: Optional maximum header line size

    :param int max_field_size: Optional maximum header field size

    :param int max_headers: Optional maximum header size

    """
    KEEPALIVE_RESCHEDULE_DELAY = 1

    __slots__ = ('_request_count', '_keepalive', '_manager',
                 '_request_handler', '_request_factory', '_tcp_keepalive',
                 '_keepalive_time', '_keepalive_handle', '_keepalive_timeout',
                 '_lingering_time', '_messages', '_message_tail',
                 '_waiter', '_error_handler', '_task_handler',
                 '_upgrade', '_payload_parser', '_request_parser',
                 '_reading_paused', 'logger', 'debug', 'access_log',
                 'access_logger', '_close', '_force_close')

    def __init__(self, manager: 'Server', *,
                 loop: asyncio.AbstractEventLoop,
                 keepalive_timeout: float=75.,  # NGINX default is 75 secs
                 tcp_keepalive: bool=True,
                 logger: Logger=server_logger,
                 access_log_class: _AnyAbstractAccessLogger=AccessLogger,
                 access_log: Logger=access_logger,
                 access_log_format: str=AccessLogger.LOG_FORMAT,
                 debug: bool=False,
                 max_line_size: int=8190,
                 max_headers: int=32768,
                 max_field_size: int=8190,
                 lingering_time: float=10.0):

        super().__init__(loop)

        self._request_count = 0
        self._keepalive = False
        self._manager = manager  # type: Optional[Server]
        self._request_handler = manager.request_handler  # type: Optional[_RequestHandler]  # noqa
        self._request_factory = manager.request_factory  # type: Optional[_RequestFactory]  # noqa

        self._tcp_keepalive = tcp_keepalive
        # placeholder to be replaced on keepalive timeout setup
        self._keepalive_time = 0.0
        self._keepalive_handle = None  # type: Optional[asyncio.Handle]
        self._keepalive_timeout = keepalive_timeout
        self._lingering_time = float(lingering_time)

        self._messages = deque()  # type: Any  # Python 3.5 has no typing.Deque
        self._message_tail = b''

        self._waiter = None  # type: Optional[asyncio.Future[None]]
        self._error_handler = None  # type: Optional[asyncio.Task[None]]
        self._task_handler = None  # type: Optional[asyncio.Task[None]]

        self._upgrade = False
        self._payload_parser = None  # type: Any
        self._request_parser = HttpRequestParser(
            self, loop,
            max_line_size=max_line_size,
            max_field_size=max_field_size,
            max_headers=max_headers,
            payload_exception=RequestPayloadError)   # type: Optional[HttpRequestParser]  # noqa

        self.logger = logger
        self.debug = debug
        self.access_log = access_log
        if access_log:
            if issubclass(access_log_class, AbstractAsyncAccessLogger):
                self.access_logger = access_log_class()  # type: Optional[AbstractAsyncAccessLogger]  # noqa
            else:
                access_logger = access_log_class(access_log, access_log_format)
                self.access_logger = AccessLoggerWrapper(access_logger)
        else:
            self.access_logger = None

        self._close = False
        self._force_close = False

    def __repr__(self) -> str:
        return "<{} {}>".format(
            self.__class__.__name__,
            'connected' if self.transport is not None else 'disconnected')

    @property
    def keepalive_timeout(self) -> float:
        return self._keepalive_timeout

    async def shutdown(self, timeout: Optional[float]=15.0) -> None:
        """Worker process is about to exit, we need cleanup everything and
        stop accepting requests. It is especially important for keep-alive
        connections."""
        self._force_close = True

        if self._keepalive_handle is not None:
            self._keepalive_handle.cancel()

        if self._waiter:
            self._waiter.cancel()

        # wait for handlers
        with suppress(asyncio.CancelledError, asyncio.TimeoutError):
            with CeilTimeout(timeout, loop=self._loop):
                if (self._error_handler is not None and
                        not self._error_handler.done()):
                    await self._error_handler

                if (self._task_handler is not None and
                        not self._task_handler.done()):
                    await self._task_handler

        # force-close non-idle handler
        if self._task_handler is not None:
            self._task_handler.cancel()

        if self.transport is not None:
            self.transport.close()
            self.transport = None

    def connection_made(self, transport: asyncio.BaseTransport) -> None:
        super().connection_made(transport)

        real_transport = cast(asyncio.Transport, transport)
        if self._tcp_keepalive:
            tcp_keepalive(real_transport)

        self._task_handler = self._loop.create_task(self.start())
        assert self._manager is not None
        self._manager.connection_made(self, real_transport)

    def connection_lost(self, exc: Optional[BaseException]) -> None:
        if self._manager is None:
            return
        self._manager.connection_lost(self, exc)

        super().connection_lost(exc)

        self._manager = None
        self._force_close = True
        self._request_factory = None
        self._request_handler = None
        self._request_parser = None

        if self._keepalive_handle is not None:
            self._keepalive_handle.cancel()

        if self._task_handler is not None:
            self._task_handler.cancel()

        if self._error_handler is not None:
            self._error_handler.cancel()

        self._task_handler = None

        if self._payload_parser is not None:
            self._payload_parser.feed_eof()
            self._payload_parser = None

    def set_parser(self, parser: Any) -> None:
        # Actual type is WebReader
        assert self._payload_parser is None

        self._payload_parser = parser

        if self._message_tail:
            self._payload_parser.feed_data(self._message_tail)
            self._message_tail = b''

    def eof_received(self) -> None:
        pass

    def data_received(self, data: bytes) -> None:
        if self._force_close or self._close:
            return
        # parse http messages
        if self._payload_parser is None and not self._upgrade:
            assert self._request_parser is not None
            try:
                messages, upgraded, tail = self._request_parser.feed_data(data)
            except HttpProcessingError as exc:
                # something happened during parsing
                self._error_handler = self._loop.create_task(
                    self.handle_parse_error(
                        StreamWriter(self, self._loop),
                        400, exc, exc.message))
                self.close()
            except Exception as exc:
                # 500: internal error
                self._error_handler = self._loop.create_task(
                    self.handle_parse_error(
                        StreamWriter(self, self._loop),
                        500, exc))
                self.close()
            else:
                if messages:
                    # sometimes the parser returns no messages
                    for (msg, payload) in messages:
                        self._request_count += 1
                        self._messages.append((msg, payload))

                    waiter = self._waiter
                    if waiter is not None:
                        if not waiter.done():
                            # don't set result twice
                            waiter.set_result(None)

                self._upgrade = upgraded
                if upgraded and tail:
                    self._message_tail = tail

        # no parser, just store
        elif self._payload_parser is None and self._upgrade and data:
            self._message_tail += data

        # feed payload
        elif data:
            eof, tail = self._payload_parser.feed_data(data)
            if eof:
                self.close()

    def keep_alive(self, val: bool) -> None:
        """Set keep-alive connection mode.

        :param bool val: new state.
        """
        self._keepalive = val
        if self._keepalive_handle:
            self._keepalive_handle.cancel()
            self._keepalive_handle = None

    def close(self) -> None:
        """Stop accepting new pipelinig messages and close
        connection when handlers done processing messages"""
        self._close = True
        if self._waiter:
            self._waiter.cancel()

    def force_close(self) -> None:
        """Force close connection"""
        self._force_close = True
        if self._waiter:
            self._waiter.cancel()
        if self.transport is not None:
            self.transport.close()
            self.transport = None

    async def log_access(self,
                         request: BaseRequest,
                         response: StreamResponse,
                         request_start: float) -> None:
        if self.access_logger is not None:
            await self.access_logger.log(request, response,
                                         self._loop.time() - request_start)

    def log_debug(self, *args: Any, **kw: Any) -> None:
        if self.debug:
            self.logger.debug(*args, **kw)

    def log_exception(self, *args: Any, **kw: Any) -> None:
        self.logger.exception(*args, **kw)

    def _process_keepalive(self) -> None:
        if self._force_close or not self._keepalive:
            return

        next = self._keepalive_time + self._keepalive_timeout

        # handler in idle state
        if self._waiter:
            if self._loop.time() > next:
                self.force_close()
                return

        # not all request handlers are done,
        # reschedule itself to next second
        self._keepalive_handle = self._loop.call_later(
            self.KEEPALIVE_RESCHEDULE_DELAY, self._process_keepalive)

    async def _handle_request(self,
                              request: BaseRequest,
                              start_time: float,
                              ) -> Tuple[StreamResponse, bool]:
        assert self._request_handler is not None
        try:
            resp = await self._request_handler(request)
        except HTTPException as exc:
            resp = Response(status=exc.status,
                            reason=exc.reason,
                            text=exc.text,
                            headers=exc.headers)
            reset = await self.finish_response(request, resp, start_time)
        except asyncio.CancelledError:
            raise
        except asyncio.TimeoutError as exc:
            self.log_debug('Request handler timed out.', exc_info=exc)
            resp = self.handle_error(request, 504)
            reset = await self.finish_response(request, resp, start_time)
        except Exception as exc:
            resp = self.handle_error(request, 500, exc)
            reset = await self.finish_response(request, resp, start_time)
        else:
            reset = await self.finish_response(request, resp, start_time)

        return resp, reset

    async def start(self) -> None:
        """Process incoming request.

        It reads request line, request headers and request payload, then
        calls handle_request() method. Subclass has to override
        handle_request(). start() handles various exceptions in request
        or response handling. Connection is being closed always unless
        keep_alive(True) specified.
        """
        loop = self._loop
        handler = self._task_handler
        assert handler is not None
        manager = self._manager
        assert manager is not None
        keepalive_timeout = self._keepalive_timeout
        resp = None
        assert self._request_factory is not None
        assert self._request_handler is not None

        while not self._force_close:
            if not self._messages:
                try:
                    # wait for next request
                    self._waiter = loop.create_future()
                    await self._waiter
                except asyncio.CancelledError:
                    break
                finally:
                    self._waiter = None

            message, payload = self._messages.popleft()

            start = loop.time()

            manager.requests_count += 1
            writer = StreamWriter(self, loop)
            request = self._request_factory(
                message, payload, self, writer, handler)
            try:
                # a new task is used for copy context vars (#3406)
                task = self._loop.create_task(
                    self._handle_request(request, start))
                try:
                    resp, reset = await task
                except asyncio.CancelledError:
                    self.log_debug('Ignored premature client disconnection')
                    break

                # Drop the processed task from asyncio.Task.all_tasks() early
                del task
                if reset:
                    self.log_debug('Ignored premature client disconnection 2')
                    break

                # notify server about keep-alive
                self._keepalive = bool(resp.keep_alive)

                # check payload
                if not payload.is_eof():
                    lingering_time = self._lingering_time
                    if not self._force_close and lingering_time:
                        self.log_debug(
                            'Start lingering close timer for %s sec.',
                            lingering_time)

                        now = loop.time()
                        end_t = now + lingering_time

                        with suppress(
                                asyncio.TimeoutError, asyncio.CancelledError):
                            while not payload.is_eof() and now < end_t:
                                with CeilTimeout(end_t - now, loop=loop):
                                    # read and ignore
                                    await payload.readany()
                                now = loop.time()

                    # if payload still uncompleted
                    if not payload.is_eof() and not self._force_close:
                        self.log_debug('Uncompleted request.')
                        self.close()

                payload.set_exception(PayloadAccessError())

            except asyncio.CancelledError:
                self.log_debug('Ignored premature client disconnection ')
                break
            except RuntimeError as exc:
                if self.debug:
                    self.log_exception(
                        'Unhandled runtime exception', exc_info=exc)
                self.force_close()
            except Exception as exc:
                self.log_exception('Unhandled exception', exc_info=exc)
                self.force_close()
            finally:
                if self.transport is None and resp is not None:
                    self.log_debug('Ignored premature client disconnection.')
                elif not self._force_close:
                    if self._keepalive and not self._close:
                        # start keep-alive timer
                        if keepalive_timeout is not None:
                            now = self._loop.time()
                            self._keepalive_time = now
                            if self._keepalive_handle is None:
                                self._keepalive_handle = loop.call_at(
                                    now + keepalive_timeout,
                                    self._process_keepalive)
                    else:
                        break

        # remove handler, close transport if no handlers left
        if not self._force_close:
            self._task_handler = None
            if self.transport is not None and self._error_handler is None:
                self.transport.close()

    async def finish_response(self,
                              request: BaseRequest,
                              resp: StreamResponse,
                              start_time: float) -> bool:
        """
        Prepare the response and write_eof, then log access. This has to
        be called within the context of any exception so the access logger
        can get exception information. Returns True if the client disconnects
        prematurely.
        """
        try:
            prepare_meth = resp.prepare
        except AttributeError:
            if resp is None:
                raise RuntimeError("Missing return "
                                   "statement on request handler")
            else:
                raise RuntimeError("Web-handler should return "
                                   "a response instance, "
                                   "got {!r}".format(resp))
        try:
            await prepare_meth(request)
            await resp.write_eof()
        except ConnectionResetError:
            await self.log_access(request, resp, start_time)
            return True
        else:
            await self.log_access(request, resp, start_time)
            return False

    def handle_error(self,
                     request: BaseRequest,
                     status: int=500,
                     exc: Optional[BaseException]=None,
                     message: Optional[str]=None) -> StreamResponse:
        """Handle errors.

        Returns HTTP response with specific status code. Logs additional
        information. It always closes current connection."""
        self.log_exception("Error handling request", exc_info=exc)

        ct = 'text/plain'
        if status == HTTPStatus.INTERNAL_SERVER_ERROR:
            title = '{0.value} {0.phrase}'.format(
                HTTPStatus.INTERNAL_SERVER_ERROR
            )
            msg = HTTPStatus.INTERNAL_SERVER_ERROR.description
            tb = None
            if self.debug:
                with suppress(Exception):
                    tb = traceback.format_exc()

            if 'text/html' in request.headers.get('Accept', ''):
                if tb:
                    tb = html_escape(tb)
                    msg = '<h2>Traceback:</h2>\n<pre>{}</pre>'.format(tb)
                message = (
                    "<html><head>"
                    "<title>{title}</title>"
                    "</head><body>\n<h1>{title}</h1>"
                    "\n{msg}\n</body></html>\n"
                ).format(title=title, msg=msg)
                ct = 'text/html'
            else:
                if tb:
                    msg = tb
                message = title + '\n\n' + msg

        resp = Response(status=status, text=message, content_type=ct)
        resp.force_close()

        # some data already got sent, connection is broken
        if request.writer.output_size > 0 or self.transport is None:
            self.force_close()

        return resp

    async def handle_parse_error(self,
                                 writer: AbstractStreamWriter,
                                 status: int,
                                 exc: Optional[BaseException]=None,
                                 message: Optional[str]=None) -> None:
        request = BaseRequest(  # type: ignore
            ERROR,
            EMPTY_PAYLOAD,
            self, writer,
            current_task(),
            self._loop)

        resp = self.handle_error(request, status, exc, message)
        await resp.prepare(request)
        await resp.write_eof()

        if self.transport is not None:
            self.transport.close()

        self._error_handler = None
